help plz.. how many cfm's?

I am currently growing in 2 tents one is 5 x 2.5 x 5 ft(veg) and the other is 4x2.5x7 ft(flower) ill be running two aircooled hoods one is a 1000w and the other a 400 plus I will have a 250 hanging vertically in the 5x2.5 I'm wondering how many cfms will I need to keep proper air exchange I'd like to go just a little overkill. I can post links to pics if needed but the way I have it set up is carbon filter hanging in flowertent connected to the 100watt hood then ducting running from the other side of the 1000 out of the tent and into the veg tent and 400watt hood out the opposite side of the 400hood up to the squirrel cage and blown out the window. I have a passive intake set up in the veg tent with a piece of ducting running from the veg tent to the flower tent. My tempstouch 84.6 in the flower tent and would like to get this down as I'm hopin for some dense nugs. Thanks in advance to any with advice I hoped this made sense. Haha. +rep

i have a 440cfm fan that is used to cool 2 1000 watters through 20 ft of 6" ducting in my flower tent... but i have a/c running constantly, and just a simple 6" intake fan, and 6" exhaust fan. temps are stable at 80-85max. you would probably be fine with 300-350, but if you like overkill.....

So say 450 cfm... Would this be overkill like too much overkill or sustainable overkill for a worry wart aiming for 75f? Lol +rep

Well now I have a problem. I'm using a dayton 4c448a which claims 465cfm and the passive intake is frsh outdoor air it topped at 52 today and my room was at 84.6 after the first two hours. Never got any higher but that's way higher than I would like it in there. What am I doin wrong here? If I should have 350 cfm and I'm at 465 with only 50f outside why am I sitting in mid 80's? Any suggestions welcome

so shoot for 1000 cfm, put a variable speed switch on the fan and dial it in to what you need.

I've considered it but the motor says its a 1 speed fan so I don't know if I can hook up a speed controller to it.

The exhaust air intake source (the carbon filter) is drawing 85 deg air to cool the lights, not to mention multiple lights in series. You can try moving your exhaust intake to draw from outside (50 deg air) which will improve the heat tansfer by using 50 deg air rather than 85.
Then you could use a much smaller exhaust fan hooked to your carbon filter for additional temp control, humidity, and air exchanges.

Also, the "1 speed" for your fan is likely just that the motor is wired with 1 speed tap instead of multiple, which is common on direct drive fans (med, low, high). You should still be able to use a solid state type fan speed controller.

Thanks for the info on the controller. How much those usually go for? If I move the exhaust intak to a fresh air source ill lose my negative pressure for the passive intake meaning I'd have to buy 2 more fans or another decent sized one to stay passive and I neither have the money nor the free space as far as amps go. I gotta unplug the entire house to use the microwave or the roomate to straighten her hair so addin more isn't an option. :/ + rep to u for the help my friend.

here's the first one i came to on ebay. $20.
http://cgi.ebay.com/Variable-FAN-SPEED-CONTROL-controller-inline-exhaust_W0QQitemZ400080587376QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5d26a94a70

Yeah...being light on available power is a bitch. The only thing I can think of, without adding, is to maybe branch ductwork from the fan inlet to each tent so you're exhausting from each tent rather than pulling from one to the other then out. You could probably get by without a carbon filter for your veg tent.

Hope I could help. Good luck!